Sequoia and Kings Canyon National Parks lie side-by-side in the southern Sierra Nevada, east of the San Joaquin Valley. Muck, who was backpacking alone, taught second grade students at
Gomes Elementary School in Fremont during the school year that ended last spring, according to principal Douglas Whipple.

Muck "was great and we really appreciated him as a teacher," Whipple said.

The past school year was the first year that Muck taught school in a classroom setting anywhere, although he had previously taught outdoor gardening classes, according to Whipple.

Muck was "an outdoors person" and "a nature lover" who is an experienced hiker, Whipple said.

Muck often used creative techniques with his students, such as having them bake bread every week so that they could learn mathematics by doing measurements, Whipple said.

Because Muck was low on the seniority list, he was assigned to teach third graders at another school in Fremont, Leitsch Elementary School, this fall, Whipple said.

He said there was an opening for Muck to stay at Gomes Elementary and "we wanted him back" but he opted for Leitsch because it would reduce his commuting time from Santa Cruz.

Whipple described Muck as "self-assured" and said school officials are hoping he is found safe.

"The kids love him," said co-worker Rudy Castillo. "He was really friendly and willing to help. He was all about protecting the environment. I hope them find him."

Muck was supposed to have returned on Aug. 17 from a backpacking trip.

According to rangers, Muck departed alone from the Roads End area of Kings Canyon National Park on Aug. 10. He planned to hike to Gardiner Basin via Gardiner Pass. After several days in the basin, he planned to hike out Gardiner Creek to Woods Creek and return to Roads End in Cedar Grove by August 17.

But he never exited the woods. The next day, his wife called for help.

NBC Bay Area's Riya Bhattacharjee and Bay City News contributed to this report.